White smoke usually denotes that it is burning coolant. The knock along with it suggests the engine is dying in a rapid fashion from a bad bearing or connecting rod. It will just get worse until it fails completely, which likely will not be very long.
Here is a guide so you can confirm the failure:
https://www.2carpros.com/articles/head-gasket-blown-test
I would take it in and get it checked but I suspect you will need some major work or a replacement engine.
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Sunday, July 23rd, 2017 AT 6:52 PM